Computing devices perform tasks by executing computing instructions. A set of computing instructions for performing a particular task form a function. A set of functions that interact when performing related tasks form an application. Two or more different applications may need to use the same function to perform the same task. While it is possible to include the same function's computing instructions in each of the applications, it is more efficient for each application to share a common set of computing instructions. By sharing a common set of computing instructions, less memory is used to store instructions, and modifications to the computing instructions need only be made in one place.
To allow more than one application to use the same functions, a library of functions, i.e., a library, is formed. Typically, each function's computing instructions and a reference to the computing instructions are placed in a library. To use a function in a library, an application invokes an operating system module that loads the library and the application calls a desired function using the reference to the function. Usually, before a loaded library can be accessed, the library must be initialized. Initialization includes executing computing instructions that, for example, build and prepare data structures used by the library.
Functions may call other functions in the same library. Functions may also call functions in another library. Hence, it is possible for a library to depend on another library. For example, an application may depend on library A that depends on library B which depends on library C. In order to load and initialize the application, libraries A, B, and C must be loaded and initialized in the proper order. The application and its libraries are typically loaded in the order that the application and libraries are discovered, i.e. in top down order. For example, the application is loaded first, then library A, then library B, etc. The application and its libraries are typically are initialized in bottom up order.
Traditionally, the process of loading and initializing libraries described above is a serial process. That is, each library must be loaded and initialized one after the other in the appropriate order. Loading and initializing can be speeded up by taking advantage of parallel processing techniques such as multithreaded processing and parallel processing hardware such as multiprocessor computing devices and multicore microprocessors.